FIG. 3 is a block diagram showing a VTR which is an example of a conventional video magnetic recording and playback device. In the figure, a video signal recording and playback means 9 records video signals on a magnetic tape 1 or reads video signals from the magnetic tape 1 by means of a rotary magnetic head 7 on a rotary drum 6. A tape travel control means 8 controls a capstan 4, a supply reel 2 and a take-up reel 3 and causes the magnetic tape 1 to travel at a constant speed. An operation control means 10 performs selection between recording and playback, and supplies the video signal recording and playback means 9 with a recording and playback control signal 11 for changing the playback state, and supplies the tape travel control means 8 with a tape travel speed control signal 12 for selecting the tape travel speed. A memory timer means 13 has a memory timer mechanism, and permits external presetting of recording and playback time, and later produces the stored contents as an operation control signal 14 for controlling preset recording or preset playback.
A shuttle switch 16 is a rotary switch which can be manually turned clockwise and counterclockwise within a certain limit, e.g., within 180 degree from a reference position (center position or 0.degree. position), and outputs specific codes, shown in FIG. 4 at (a), corresponding to the switch position. A jog switch 17 is also a rotary switch which can be manually turned clockwise or counterclockwise, without limit, and outputs a pulse signal, shown in FIG. 4 at (b), each time it is rotated a predetermined angle, e.g., 90 degrees. An encoder 18 encodes the output from the shuttle switch 16, and, only at one reference position, e.g., the center position (0.degree. position), of the shuttle switch 16, encodes the pulse signal from the jog switch 17 and outputs the encoded data as the jog-shuttle data 19.
A playback control mode selecting switch 23 is closed in the playback control mode and is opened in the presetting mode. A timer presetting mode selecting switch 24, on the other hand, is closed in the presetting mode and is opened in the playback control mode.
The shuttle switch 16 and the jog switch 17 are used for two purposes. When the playback mode selecting switch 23 is closed and the presetting mode selecting switch 24 is opened, the data from the shuttle switch 16 and the jog switch 17 are supplied to the operation control means 10, and the shuttle switch 16 and the jog switch 17 are used for controlling the playback operation. When the presetting mode selecting switch 24 is closed and the playback control selecting switch 23 is opened, the data from the shuttle switch 16 and the jog switch 17 are supplied to the memory timer means 13, and the shuttle switch 16 and the jog switch 17 are used for inputting the present data.
Further details of the manipulation of the switches in the playback control mode is given below:
The playback can be performed in various modes including Forward Slow Playback, Forward Normal-speed Playback, Forward Double Playback, Reverse Slow Playback, Reverse Normal-speed Playback, Reverse Double Playback, and Still/Frame Advancement Playback. To select one of these modes, the shuttle switch is rotated to the corresponding position. The relationship between the position of the shuttle switch 16 and the selected mode of playback is as follows:
______________________________________ Position Selected Mode (Range of Angles) of Playback ______________________________________ +10.degree. to +20.degree. Forward Slow Playback +20.degree. to +30.degree. Forward Normal-speed Playback +30.degree. to +40.degree. Forward High-speed Playback -10.degree. to -20.degree. Reverse Slow Playback -20.degree. to -30.degree. Reverse Normal-speed Playback -30.degree. to -40.degree. Reverse High-speed Playback 0.degree. Still/Frame Advance Playback ______________________________________
Here, the sign "+" indicates the angle attained when the shuttle switch is rotated clockwise from a reference position, i.e., the center position (0.degree.), while the sign "-" indicates the angle attained when the shuttle switch is rotated counterclockwise from the reference position.
When the shuttle switch 16 is at the center position, the Still Playback for reproducing a still picture is performed. When the jog switch 17 is also manipulated, Frame Advance Playback is effected. That is, each time the jog switch 17 is rotated by one click the picture is advance by one frame. The direction of advancement is forward when the jog switch 17 is rotated clockwise, and is backward when the jog switch 17 is rotated counterclocksise.
In this way, the mode of playback and hence the speed of the playback is decided on the basis of the range of angle in which the shuttle switch 17 is set at.
The shuttle switch 16 produces data indicating its position, which is supplied to the encoder 18, from which the playback control signal 21 for designating Forward Slow, Forward Normal-speed Playback, Forward High-speed (e.g., Double-speed) Playback, Reverse Slow, Reverse Normal-speed Playback, Reverse High-speed (e.g., Double speed) Playback, or Still/Frame Advance Playback is produced and supplied to the operation control means 10.
When the shuttle switch 16 is at the reference position, and the jog switch 17 is rotated, a pulse signal is supplied to the encoder 18 each time the jog switch 17 is rotated a predetermined angle, e.g., 90 degree. The pulse signal from the jog switch 17 is encoded, and a playback control signal 21 for Frame Advance Playback is supplied from the encoder 18 to the operation control means 10. During Frame Advance Playback, one pulse signal from the jog switch 17 causes the advancement of the picture by one frame.
In accordance with the playback control signal 21, the operation control means 10 supplies the video signal recording and playback means 9 with the recording and playback control signal 11 to select the playback state, and supplies the tape travel control means 8 with the tape travel speed control signal 12 to select the tape travel speed to perform Forward Slow Playback, Forward Normal-speed Playback, Forward High-speed Playback, Reverse Slow Playback, Reverse Normal-speed Playback, Reverse High-speed Playback, or Still/Frame Advance Playback.
Manipulation of the switches in the presetting mode will now be described in detail.
This presetting is made while the VTR is in the stop state. In this mode, the item on which presetting is to be preset is selected by manipulation of the shuttle switch 16. The items for presetting may, for example, include the following:
Channel Number (of which a program is to be recorded) PA0 Date (on which recording is to be made) PA0 Starting Hour (at which the recording is to be started) PA0 Starting Minute (at which the recording is to be started) PA0 Ending Hour (at which the recording is to be ended) PA0 Ending Minute (at which the recording is to be ended)
These items are selected in turn by the following manipulation of the shuttle switch. Assuming a first item, e.g., the Channel Number, is being selected, if the shuttle switch is rotated from the reference position clockwise to a predetermined angle, e.g., 15.degree., i.e., one click, and is returned to the reference position, then a next succeeding item, e.g., the Date, is selected. If the shuttle switch is again rotated clockwise, by the same predetermined angle and then returned, the next item, e.g., the Starting Hour is selected. When the preceding item needs to be selected, the shuttle switch 16 is rotated by a predetermined angle counterclockwise, and then returned to the reference position.
While each item is selected, the setting of a numerical value, such as the numerical indication of the channel number, date, or starting hour, for the item is input by means of the jog switch 17. Before the manipulation of the setting is begun, an arbitrarily value is given, (For instance, the value which was set in the last presetting is given). Starting with this initial value, the numerical value is incremented or decremented by manipulation of the jog switch 17. Each time the jog switch 17 is rotated clockwise by the predetermined angle, the value is incremented. Each time the jog switch 17 is rotated counterclockwise by the predetermined angle, the value is incremented.
The numerical values for the respective items are supplied, as the presetting data 22, to the memory timer means 13 and stored.
More specifically, responsive to the manipulation of the shuttle switch 16, the code indicating the selected item is produced by the encoder 18, and is supplied through the presetting mode selecting switch 24 to the memory timer means 13. When the shuttle switch 16 is fixed at the reference position and the jog switch 17 is rotated so that for rotation of each predetermined angle, a pulse signal is output to the encoder 18 and is encoded, and the presetting data 22 for setting the numerical value, such as recording and playback time, is supplied from the encoder 18 to the memory timer means 13.
Once the presetting has been made, the memory timer means 13 keeps comparing the current time as counted by the internal timer mechanism (built within the memory timer means 13) with the starting time (date, hour and minute) stored in the memory timer 13 and when they coincide, it issues a start command signal, which is then supplied to the operation control means 10, together with other data such as the data indicating the channel of which a program is to be recorded. In accordance with these data, the operation control means 10 controls the video signal recording and playback means 9 and the tape travel control means 8 to cause starting of the recording.
While a program is being recorded, the memory timer means 13 keeps comparing the current time as counted by the internal timer mechanism with the ending time (hour and minute) stored in the memory timer 13, and when they coincide, it issues a stop signal, which is then supplied to the operation control means 10. In accordance with this stop signal, the operation control means 10 controls the video signal recording and playback means 9 and the tape travel control means 8 to stop the recording. When the presetting step is manipulated to select Playback (rather than Recording), a similar control for starting and ending playback is performed by the action of the memory timer means 13, the operation control means 10, the video signal recording and playback means 9 and the tape travel control means 8.
The VTR in the prior art is constructed as described above, and mode selection switches 23 and 24 may have to be manipulated to alter the mode before using the shuttle switch and the jog switch for either of the two modes. The manipulation of the VTR is therefore troublesome.